This invention relates generally to a window assembly and, more particularly, to a window assembly which is especially suitable for use in the cab of a rugged off-the-road vehicle of the type used in the construction and agricultural industry. Such vehicles (e.g., crawler-type tractors) are frequently subjected to severe shock loads and vibratory forces during the performance of heavy duty work.
Modern off-the-road construction and agricultural have enclosed cabs which are adapted to be heated and air conditioned to provide comfort for the operator during year around use of the vehicles. Because such a vehicle often is operated in potentially dangerous conditions and must be carefully maneuvered around close obstacles, it is necessary that the cab be provided with multiple windows of extensive area in order to permit the operator to easily view the surrounding conditions on all sides of the cab.
As a result of heat transfer through the extensive window area, difficulty is encountered in comfortably heating or cooling the cab during extreme weather conditions. This problem could be alleviated by utilizing thermal insulated windows of the type comprising multiple glass panels separated by spacer means and suitably sealed to establish a dead air space between the panels. Insulated glass window assemblies, however, have not been used successfully in most commercially available off-the-road construction vehicles because the window assemblies are subjected to the high shock loads and severe vibrations which occur during operation of the vehicle. With a conventional insulated window assembly, the vibrations and shock loads acting on the window assembly destroy the integrity of the seal between the panels in a relatively short period of time. Once the seal has been ruptured, water vapor may enter and condense within the space between the panels and will soon create a visibility-impeding film which cannot be easily cleaned from the window assembly.
Accordingly, while there is a need for insulated multi-panel window assemblies in off-the-road construction vehicles and the like, such vehicles typically have been equipped with single panel windows. A single panel window not only impedes efficient heating and cooling of the cab but also forms a relatively poor noise barrier. In addition, a single panel window is comparatively susceptible to breakage by rocks, tree limbs and the like encountered in the construction and farming environments and thus can present a potential injury hazard to the operator of the vehicle.